Zbrasov Aragonite Caves

The Zbrasovske aragonitove jeskyne are hydrothermal: they were dissolved not by rainwater sinking from above but by warm mineral water and carbon dioxide rising from below, which is unusual and gives them their two distinguishing features. They are the warmest caves open in the country, staying around fourteen degrees all year, and they contain accumulations of carbon dioxide gas that pool in hollows and low chambers - the gas is heavier than air and lies in invisible lakes on the floor, monitored constantly, with parts of the system closed because of it. The decoration is aragonite rather than the usual calcite, forming needle and shrub-like clusters, along with sinter and geyser-type formations. Above the caves is the Hranicka propast, an abyss whose flooded shaft has been probed by divers and remote vehicles past four hundred metres and is among the deepest known freshwater cavities in the world.

What you actually see

• Warm caves - around fourteen degrees all year, dissolved by rising mineral water.
• Carbon dioxide lakes - invisible gas pooling in hollows, monitored constantly.
• Aragonite clusters - needle and shrub forms rather than ordinary dripstone.
• Hranicka propast above - a flooded abyss among the deepest known in the world.

When to go

All year. Two hours.

Honest expectations

Guided tours only and busy in summer. Parts of the system are permanently closed because of the gas. The abyss itself is not visitable - it is viewed from a platform above. Steps throughout.

Nearby

Teplice nad Becvou spa is at the entrance; Hranice is three kilometres away.